Falls affect millions of people each year and result in significant injuries, particularly among the elderly. In fact, it has been estimated that falls are one of the top three causes of death in elderly people. A fall is defined as a sudden, uncontrolled and unintentional downward displacement of the body to the ground, followed by an impact, after which the body stays down on the ground.
A personal emergency response system (PERS) is a system in which help can be assured. By means of Personal Help Buttons (PHBs) the user can push the button to summon help in an emergency. A majority of calls are because the user has fallen. Also, if the user suffers a severe fall (for example by which they get confused or even worse if they are knocked unconscious), the user might be unable to push the button, which might mean that help doesn't arrive for a significant period of time, particularly if the user lives alone. The consequences of a fall can become more severe if the user stays lying for a long time.
Fall detection systems are also available that process the output of one or more movement sensors to determine if the user has suffered a fall. Most existing body-worn fall detection systems make use of an accelerometer (usually an accelerometer that measures acceleration in three dimensions) and they are configured to infer the occurrence of a fall by processing the time series generated by the accelerometer. Some fall detection systems can also include an air pressure sensor, for example as described in WO 2004/114245, for measuring the height, height change or absolute altitude of the fall detection system.
In general, a fall detector tests on features like impact, orientation, orientation change, height change, vertical velocity, and alike. Reliable detection results when the set of computed values for these features is different for falls than for other movements that are not a fall.
Typically, when a fall is detected by the fall detection system, an alarm signal is transmitted to a remote call centre, from where an operator can arrange for assistance (e.g. the emergency services, a care provider or a family member) to be sent to the user. In other cases, if the fall detection system is provided with suitable communications functionality, the fall detection system can contact the emergency services, a care provider or a family member directly.
In some cases a revocation period is applied when a fall is detected which allows a short period (e.g. 1 minute) for a user to stand up after a fall has occurred (and been detected by the fall detection system) before the alarm is triggered or sent to the remote call centre.